My Porsche Story: the 996 C4S RWD conversion
As part of our series where 9WERKS members share their Porsche story, Mike Willis explains his 996 C4S rear-wheel-drive conversion – and how you can do it too…
Like many of us when looking at a new car, especially something like a 911, you browse the marketplace, researching the models, specs and values for what seems like eternity! I had always loved the 996 Carrera 4S with its Turbo hips and the subtly more aggressive styling. After a lot of searching (and a dilemma with a really tempting Cayman) I finally settled on a manual C4S in Basalt black, which was within budget, and collected the car on my birthday (what a great way to celebrate!).
The 996 is one of the most diversified models of car you can buy. Porsche offered the 996 as a Cabriolet, Targa or Coupe, in narrow and wide body styles, rear wheel drive and four wheel drive. Then there’s the Carrera 4S and Turbo, not forgetting the track-oriented GT3, GT3 RS and GT2 models. But there is also a glaring omission in the 996’s line up, a model which was present in both the predecessor and successor model ranges. A 911 Carrera S.
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I’ve always enjoyed tinkering with cars, making them more individual and making small enhancements with aftermarket parts and feeling the improvement they bring. After about six months of ownership a routine service highlighted that one of my front CV boots had split, depositing its grease all over the inside of the wheel. As I would need to remove the drive shaft to repair the CV boot, this gave me the impetus to investigate what it would take to remove the front wheel drive system and run the car as rear wheel drive, a la ‘Carrera S’. Some time spent on Google led me to believe that converting the car wouldn’t actually be too hard.
The four wheel drive system on the 996 is purely mechanical, which means there are no electronics involved in distributing the drive to the front axle, or ECU reprogramming required. Between 5% and 40% of torque is sent to the front axle via a clutch pack, which senses a difference between front and rear axle rotation.
The conversion to rear wheel drive brings a number of benefits, some small and some more noticeable. Firstly there are the performance benefits. The drive train has less rotational mass, meaning that the engine doesn’t have to work so hard to move the car. There is less weight, as the drive shafts, prop shaft and differential housing add up to 45kgs, which you’re lugging around wherever you go. There are also smaller benefits in things like better fuel economy, extended clutch life and improvements in steering feel and feedback. It’s also easier to change gear, which I put down to less resistance on the transmission.
The one final benefit is that it’s completely reversible, and costs nothing to do!
The main stages to convert an AWD 996 into a RWD one are:
- Crack off the hub nuts on the front hubs
- Jack the car up as high as possible (remember, you have to have enough room to take out the bulky differential housing)
- Remove all under trays
- Temporarily remove the gearbox mount so you can access the six bolts of the rubber flex disc (also known as ‘the doughnut’) and then bolt the mount back in place
- Slide out the prop shaft
- Some underbody braces need to be temporarily removed to access the differential
- Undo the inner driveshaft bolts to the diff housing
- Undo the diff housing to body bolts and carefully remove the differential
- Remove drive shafts
The next bit is probably the trickiest. You need to break down the outer CV joints on the drive shafts. The reason you do this is because the car needs to measure front wheel rotation for things like the ABS and PSM systems. It does this using the reluctor ring on the external face of the CV joint. It's quite fiddly, and probably worth purchasing some replacement drive shafts if you don’t want the hassle of rebuilding them to return to full 4WD in future.
Obviously a full geo is then recommended as with less weight at the front the camber is likely to be out of alignment. I would also recommend adjustable coilover suspension to readjust the ride height at the front of the car – although it’s barely different to stock in reality.
I now have a widebodied, rear-wheel-drive 996 Carrera 2S! I’ve driven the car in this configuration for about 18 months and it’s been fantastic. No ill effects, but only a number of benefits. I’ve even taken the car on track a few times, and it’s performed great. You really have to be pushing the limit extremely hard to break the 295 -section rear tyres with 320hp, even on track or in wet conditions. The only downside is I have lost a shelf in the garage to all the front wheel drive bits I removed!
Want to tell your story? Email us hello@9werks.co.uk.
Want to tell your story? Email us hello@9werks.co.uk.